Porcelain casing bead construction



Dec. 12, 1967 Filed March 5, 1966 J- R. GAMBLE PORCELAIN CASING BEADCONSTRUCTION 5 Sheets-Sheet 1 FIG. 5.

WiTNESSES: j W

INVENTOR v James R. Gamble ATTORNEY Dec. 12, 1967 J. R. GAMBLE PORCELAINCASING BEAD CONSTRUCTION 3 Sheets-Sheet 2 Filed March 5, 1966 FIG-9.

FIG.8.

Dec. 12, 1967 J. R. GAMBLE PORCELAIN CASING BEAT) CONSTRUCTION FiledMarch 3, 1966 3 Sheets-Sheet 5 FIG. 6

FIG. 7.

United States Patent 3,358,073 PORCELAIN CASING BEAD CONSTRUCTION JamesR. Gamble, Unity Township, Greensburg, Pa., assignor to WestinghouseElectric Corporation, Pittsburgh, Pa., a corporation of lennsylvaniaFiled Mar. 3, 1966, Ser. No. 531,598 6 Claims. (Cl. 174-137) ABSTRACT OFTHE DISCLOSURE To enable a much better securement of a metallic mountingflange to the end of a porcelain casing, the end of the porcelain casinghas a formed bead construction of particular dimensions and curvatures.In more detail, the bead height (H) should be between 0.06 inch and 0.12inch, the bead spacing (S) between 0.38 inch and 1.00 inch, and theradius of curvature (R of the individual beads should be between 0.06inch and 0.15 inch. The curvature (R extending from the crest of eachbead to the root thereof should vary between 0.12 inch to 0.38 inch. Thebead curvature (R should have the following relationship with respect tothe bead height (H): R 517.

This invention relates generally to porcelain casing bead constructionand, more particularly, to an improved casing bead construction for aporcelain casing adaptable for use in lightning-arrester applications,for example.

A general object of the present invention is to provide an improved beadconstruction for a porcelain casing which greatly enhances the effectivestrength of the joint between a porcelain casing and an associatedmetallic mounting flange ring.

A further object of the present invention is to provide an improved beadconstruction for a porcelain casing which will eliminate crackingbetween adjacent beads and, in addition, will reduce costs ofmanufacture by eliminating rejects, and generally will facilitate themanufacture of sound, high-quality, porcelain casings.

Still a further object of the present invention is the provision of animproved casing bead construction which is adaptable to high-volumeproduction, and which will diminish the possibility of operator errorand, in addition, will obviate the need for additional secondarytooling. Still a further object of the present invention is theprovision of an improved end construction for a porcelain casing whichwill result in a secure attachment of the associated metallic flangering.

In order to attach a flange to a porcelain cylinder with Fortland cementor sulphur base cement, it is necessary to roughen the outer surface ofthe porcelain in the area of flange attachment. The most common methodof accomplishing this is to use a sanded surface attached to theporcelain surface with glaze.

There are some applications where the use of a sanded surface is notpractical and for these applications, previous solutions have been theuse of a knurled surface, ground grooves or closely spaced, sharplydefined beads that approximated the appearance of the sand band. Theseclosely spaced, sharply defined beads were the most common.

All of these solutions suffer from one serious defect in that they aresources of stress concentration. Stress concentrations occur at pointson the surface where there is some sort of discontinuity. The closelyspaced, sharply defined beads, in particular, have an adverse effect onthe load-carrying ability of a porcelain assembly. They introducesources of high stress concentration in several ways: (a) Theirconfiguration, using very sharp radii and abrupt changes in section,result in sharp discontinuities which increase the magnitude of stressconcentration. (b) During drying of a porcelain part, shrinkage takesplace. These sharp, closely spaced beads or projections will dry morerapidly than adjoining heavy sections. A tensile stress results whichtends to cause cracks at the spot where the contrasting sections meet.(c) During machining of the porcelain part, these small projections arerelatively fragile and are subject to small tears or cracks that resultfrom the loads applied during machining.

These sources of stress concentration greatly affect the load-carryingproperties of brittle materials such as porcelain. The final fracetureof brittle material is the direct result of a localized failure. Thislocalized failure is most likely to occur at some point of stressconcentration. In order to reduce the degree of stress concentrationthat results from discontinuities, it is necessary to blend as graduallyas practicable so as to alleviate the sharp discontinuities.

According to one aspect of the present invention, a bead construction isprovided having particular dimensional limits, and resulting in astress-free attachment to the associated metallic mounting flange ring.This is accomplished by the use of formed beads of particularconfiguration, spacing and height, provided on the ends of theinsulating casing element to coact with the cement to fixedly secure theassociated end casting rigidly into position.

The advantages of the type of bead construction of the present inventionare:

First, it minimizes the degree of stress concentration. Second, it iseasier to machine. Third, it increases the effective strength of theporcelain casing.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings, inwhich:

FIGURE 1 is a side elevational view of a porcelain casing embodying theprinciples of the present invention, with a quarter section removed tomore clearly illustrate the bead configuration;

FIGS. 2-4 are fragmentary cross-sectional views of limiting beadconstructions which may be provided at the ends of the porcelain casingof FIG. 1 illustrating a certain leeway of dimensional relationships;

FIG. 5 is a fragmentary sectional view indicating the attachment of amounting flange ring through a cemented construction with the beaded endof the associated porcelain casing;

FIG. 6 is a top plan view 0 fan end casting, which is employed toencircle the end of an associated porcelain casing;

FIG. 7 is a sectional view of the metallic flange ring of FIG. 6, takensubstantially along the line VII-VII of FIG. 6;

FIG. 8 illustrates a modified construction involving a taperedenlargement of the end portion of a porcelain casing for increasedstrength in attachment; and,

FIG. 9 illustrates, in side elevation, a complete high voltagelightning-arrester assembly, indicating the superpositioning of severalarrester sections, each of which embodies principles of the presentinvention.

The present invention is particularly concerned with a novel beadconstruction, which prevents stress concentration at the beads. As wellknown by those skilled in the art, it is necessary to provide anattachment arrangement which results in a strong joint with favorabledistribution of the stress between the jointing material and theporcelain casing.

With particular reference to the drawings, it is noted that FIGURE 1illustrates a side elevational view of a Edward F. W. Beck and OttoAckermann, and assigned to the assignee of the instant application, as atypical example of use of a cemented joint construction between aporcelain outer casing and a metallic mounting flange element, whichencircles each end of the casing.

FIG. 2 illustrates in vertical section, and fragmentarily, the improvedbead construction 2 of the present invention, as applied to theporcelain casing element 1 of FIG. 1. The dimensional relationships areindicated in the figure and have been found to provide a stress-freeattachment.

Using the bead construction 2 of the present invention, the effectivestrength in tension of the joint between the end support casting 4 andthe porcelain casing increased from approximately 16,000 pounds to43,000 pounds using the same porcelain and flange assembly with the onlychange being the bead construction 2.

FIGS. 2-4 illustrate the dimensional limits which are to be applied totake advantage of the improved stressfree bead construction 2 of thepresent invention. It is to be noted that the bead height H may rangebetween .06 inch to .12 inch, the bead spacing 8 may range between .38inch to 1.00 inch, the bead spacing S being approximately equal to 6 Rwhich is the radius of the curvature of the individual beads 3.

It is desirable to make R equal to or greater than H, a preferable rangebeing from .06 inch to .15 inch. The radius R of the curved surfacespreferably ranges between .12 inch to .38 inch, but may be as large asconveniently possible.

It is to be noted that FIGS. 2-4 illustrate the lower limit, mostpractical dimensions, and the practical upper limit to clearly indicatethe dimensional limits of the bead construction 2 of the presentinvention.

FIG. 5 fragmentarily illustrates, partially in section, the cementedattachment of a metallic end ring 4 with the end 8 of a porcelaincasing 1. As well known by those skilled in the art, the end casting 4-may be securely fastened to the end of the porcelain casing 1 byMineralead cement 10, a high-melting-point sulfur cement, which containsno corrosive constitutents.

The formulation of the Mineralead cement is as fo1 lows:

Material: Content, percent Refined sulfur, min. Inert aggregate 35-45Plasticizer, max 3 1 NoTE.-Suitable nonvolatile plasticizer insufficient quantity so that cement conforms to requirements of thisspecification.

Inert aggregate composition The chemical composition of the inertaggregate shall conform to the following:

Chemical: Content, percent Carbon 1.0 to 2.0 SiO 97.0- to 98.5 A1 0 0.3to 0.7 Fe O 0.1 to 0.5 CaO none MgO none K 0 none NazO i none NaCl orother inorganic halides none Instead of Mineralead, a Portland cementcould be used in the lightning arrester casing construction. This cement10 has been found to be extremely strong, as shown by cantileverstrength tests, and preferably contains a plasticizer, which preventsmechanical stresses. As well known by those skilled in the art, the endcastings 4 may be formed of an aluminum alloy and have considerablemechanical strength to support the lightning arrester and, additionally,provide a means of stacking units to form a column. The purpose andfunction of a lightning arrester device is set forth in detail in theaforesaid US. Patent No. 2,858,476, which may be referred to in thisconnection.

FIGS. 6 and 7 respectively illustrate top and vertical sectional viewsof a typical metallic end support casting 4. It will be noted that thesupport casting 4 (FIG. 7) has internally-provided beads 41;, whichcooperate with the cement 10 to provide a secure attachment. It willmoreover be noted that the end flange support ring 4 hasoutwardly-extending mounting ears 4b with mounting apertures 40 providedtherein, which may accommodate mounting bolts, not shown.

FIG. 8 illustrates a modified construction of a porcelain insulatorcasing 1a having a tapered enlarged end portion 12, which additionallymay be provided to increase the strength of attachment. It is to benoted that the end 12 of the casing section 1a is tapered so as toincrease the resistance of the metallic end flange ring 4 from pullingoff of the end of the insulator casing in.

FIG. 9 illustrates in side elevation a self-supporting high-voltagelightning-arrester. For the higher voltages, say, for example, 336 kv.,the lightning-arrester assembly 20 may have a height A of 239.5 inchesand a grading ring radius B of 164 inches. The weight of the assembly 20may, for example, be 2643 pounds. It is evident, therefore, that windstresses, weight loading and other forces come into play to result inheavy cantilever loading forces being imposed upon thelightning-arrester assembly 20, and the attachments between theporcelain casings 1 and the end castings 4, the latter bolted together,must be secure and not loosen during the operational life of the device.The bead construction 2 of the present invention has overcome thissevere problem, and has provided a secure attachment between the casingelements 1 and the end castings 4.

Although there has been illustrated and described specific structures,it is to be clearly understood that the same were merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art without departing from the spiritand scope of the invention.

I claim as my invention:

1. An insulating cylindrical porcelain casing having anexternally-provided circumferentially-extending bead configurationadaptable to fixedly secure an encompassing mounting flange ring, or thelike, by a cemented construction, said bead configuration providing abead spacing between 0.38 inch and 1.00 inch and a bead height between0.06 inch and 0.12 inch.

2. The insulating cylindrical porcelain casing according to claim 1,wherein the beads in cross-section have a circular configuration with aradius of curvature (R of between 0.06 inch and 0.15 inch.

3. The insulating cylindrical porcelain casing according to claim 2,wherein the curvature (R extending from the crest of each bead to theroot thereof varies from 0.12 inch to 0.38 inch.

4. An insulating cylindrical porcelain according to claim 1 wherein saidhead configuration provides a bead spacing (S) of substantially 0.75inch with a bead height (H) of substantially 0.09 inch.

5. The combination of claim 4, wherein the curvature (R extending fromthe crest of each head to the root thereof is substantially 0.3 8 inch.

6. An insulating cylindrical porcelain casing having anexternally-provided circumferentially-extending bead configurationadaptable to fixedly secure an encompassing mounting flange ring, or thelike, by a cemented construction, said bead configuration providing abead spacing 5 a 6 (S) which is approximately equal to 6R ,where (R isFOREIGN PATENTS the radius of curvature of the individual beads. 300,41911/1928 Great Britain.

References Cited OTHER REFERENCES UNITED STATES PATENTS 5 Picard, Germanapplication No. 1,097,502, published 1,812,713 6/1931 Proctor et a1.28789.365X 2,542,798 2/1951 Cumming 1'7 15 X LARAMIE E. ASKIN, PrimaryExaminer.

1. AN INSULATING CYLIDRICAL PORCELAIN CASING HAVING ANEXTERNALLY-PROVIDED CIRCUMFERENTIALLY-EXTENDING BEAD CONFIGURATIONADAPTABLE TO FIXEDLY SECURE AN ENCOMPASSING MOUNTING FLANGE RING, OR THELIKE, BY A CEMENTED CONSTRUCTION, SAID BEAD CONFIGURATION PROVIDING ABEAD SPACING BETWEEN 0.38 INCH AND 1.00 INCH AND A BEAD HEIGHT BETWEEN0.06 INCH AND 0.12 INCH.